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Athlete's Heart vs HCM — EECC MCQ

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HardCardiomyopathyAthlete's Heart vs HCMEECC

During an EP study of regular narrow-complex tachycardia, a premature ventricular stimulus delivered when the His bundle is refractory terminates the tachycardia without atrial activation. What mechanism does this prove?

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Correct answer: C — Orthodromic atrioventricular re-entry using a concealed accessory atrioventricular pathway

A His-refractory ventricular premature beat cannot enter an AV-nodal circuit through the refractory His–Purkinje system. Termination without atrial activation proves that the ventricle and an accessory atrioventricular pathway are required components of the circuit, establishing orthodromic AVRT rather than AVNRT or an atrial/automatic tachycardia.

Reference: 2019 ESC Guidelines for supraventricular tachycardia. https://academic.oup.com/eurheartj/article/41/5/655/5556821